1. Field of the Invention
The invention relates to a contact arrangement for a switch, especially a vacuum switch or circuit breaker, having two coaxially positioned contacts.
2. Description of the Prior Art
It is known to prevent an increase in arc voltage and the associated high power transfer in switches by means of a coaxially magnetic field in the air gap between the opened contacts. For this purpose, a coil can be employed which cylindrically surrounds the switch housing, is arranged electrically in series with the switch contacts and which builds up a current-dependent axial magnetic field that permeates the gap between the contacts. In order to increase the field strength in the contact gap, the coil may be built up in a double layer with the windings running back and forth in helical fashion. The manufacture of such switches, however, entails a relatively high cost. An example of such an arrangement is disclosed in German Offenlegungsschrift DE-OS No. 29 11 706.
As shown by German Offenlegungsschrift DE-OS No. 25 46 376, contact arrangements for vacuum switches having planar contacts are known wherein the contacting surfaces of the contacts form circuit surfaces concentrically surrounded by a burn-off region. A planar cavity containing a ferromagnetic insert is positioned between each contact surface and the associated electrical connector lead. The plate-like insert is arranged radially of the arc to develop a radial current component having a force component which drives the arc radially outward toward the burn-off region of the contact.
Moreover, as disclosed in German Patent DE-PS No. 1 196 751, vacuum switches, are known which have cup-shaped contacts, the bases of which are connected to current leads and the rims of which present ring-shaped contacting surfaces. The annular walls of both contacts are configured with oppositely directed slanted slits which divide the walls into individual segments. These segments develop a current loop with the arc whose Lorenz forces cause the arc to be rotated between the contacts.